PART 1 DEALS WITH THE DYNAMIC ASPECTS OF THE SUBJECT: MATHEMATICAL ANALYSIS OF SYSTEMS SUBJECTED TO INDEPENDENT VIBRATIONS BY MEANS OF MATHEMATICAL MODELS. THE ANALYTICAL SYSTEMS USED ARE NON-LINEAR SYSTEMS, HYDRODYNAMICS AND NUMERICAL METHODS. PART 2 EXAMINES SEISMIC MOVEMENTS, THE DYNAMIC BEHAVIOUR OF STRUCTURES AND THE BASIC CONCEPTS OF THE SEISMIC DESIGN OF STRUCTURES.

Fundamentals of earthquake engineering

An alternative to the Mononobe–Okabe equations for seismic earth pressures

An experimental and analytical program was designed and conducted to evaluate the magnitude and distribution of seismically induced lateral earth pressures on cantilever retaining structures with dry medium dense sand backfill. Results from two sets of dynamic centrifuge experiments and two-dimensional nonlinear finite-element analyses show that maximum dynamic earth pressures monotonically increase with depth and can be reasonably approximated by a triangular distribution. Moreover, dynamic earth pressures and inertia forces do not act simultaneously on the cantilever retaining walls. As a result, designing cantilever retaining walls for maximum dynamic earth pressure increment and maximum wall inertia, as is the current practice, is overly conservative and does not reflect the true seismic response of the wall-backfill system. The relationship between the seismic earth pressure increment coefficient (ΔK AE ) at the time of maximum overall wall moment and peak ground acceleration obtained from our experiments suggests that seismic earth pressures on cantilever retaining walls can be neglected at accelerations below 0.4 g. This finding is consistent with the observed good seismic performance of conventionally designed cantilever retaining structures.

Seismic Earth Pressures on Cantilever Retaining Structures

The precise estimation and forecast of the safety factor (SF) in civil engineering applications is considered as an important issue to reduce engineering risk. The present research investigates new artificial intelligence (AI) techniques for the prediction of SF values of retaining walls, as important and resistant structures for ground forces. These structures have complicated performances in dynamic conditions. Consequently, more than 8000 designs of these structures were dynamically evaluated. Two AI models, namely the imperialist competitive algorithm (ICA)-artificial neural network (ANN), and the genetic algorithm (GA)-ANN were used for the forecasting of SF values. In order to design intelligent models, parameters i.e., the wall thickness, stone density, wall height, soil density, and internal soil friction angle were examined under different dynamic conditions and assigned as inputs to predict SF of retaining walls. Various models of these systems were constructed and compared with each other to obtain the best one. Results of models indicated that although both hybrid models are able to predict SF values with a high accuracy and they can be introduced as new models in the field, the retaining wall performance could be properly predicted in dynamic conditions using the ICA-ANN model. Under these conditions, a combination of engineering design and artificial intelligence techniques can be used to control and secure retaining walls in dynamic conditions.

Assessing Dynamic Conditions of the Retaining Wall: Developing Two Hybrid Intelligent Models

In this paper, a combination of artificial neural network and ant colony optimization (ANN-ACO) was used for dynamic conditions of retaining wall structures. The retaining walls produce different responses to dynamic loads. The applied data of this study comprising of wall height and thickness, soil density, internal friction angle, and stone density. The walls were designed in a variety of dynamic conditions. Various conditions were considered for the design of the retaining wall structures. Then, an extended data set was created for the next step. After that, the new systems were implemented using optimized artificial intelligence techniques. The neural network provided strong relationships between various wall parameters. The design of various networks in the present research led to the best evaluation of the dynamic conditions of the retaining walls. Under these conditions, an ACO was used for optimal design. Effects of parameters varied due to different wall conditions when dynamic loads were considered. Therefore, the impact of parameters was evaluated using hybrid ANN-ACO to increase the efficiency. These designs provided more control over dangers by dynamic loads of a retaining wall structure.

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Improving Performance of Retaining Walls Under Dynamic Conditions Developing an Optimized ANN Based on Ant Colony Optimization Technique

Seismic Soil Pressure for Building Walls-An Updated Approach

This paper presents a performance-based seismic analysis and design of a large suspension bridge, the new Tacoma Narrows Parallel Crossing in the State of Washington. The scope of the project included establishment of design criteria, extensive analysis and validation of the design. The analysis was performed using detailed three-dimensional models that included geometric and material non-linearity. The target post-earthquake level of service was verified using stress, deformation and ductility criteria. In the absence of well-established criteria, which relate the structural response of tower shafts to specific levels of performance, capacity analyses were performed to demonstrate that the design fulfills the performance objectives. The seismic analysis and design of this bridge was reviewed throughout the design process. An independent check team also performed separate analysis and validation of the design. Thus, this bridge constitutes an example of a large-scale design project where the performance-based seismic design procedures underwent rigorous assessment. This work demonstrated that the performance-based approach for seismic design is an appropriate way for designing earthquake-resistant structures. Further data that relate the structural response with the performance objectives are necessary. Copyright © 2005 John Wiley & Sons, Ltd.

Farhang Ostadan

Papers

Seismic Soil Pressure for Building Walls-An Updated Approach

Performance‐based seismic analysis and design of suspension bridges

Probabilistic and deterministic soil structure interaction analysis including ground motion incoherency effects

Effects of structural nonlinearity and foundation sliding on probabilistic response of a nuclear structure

Consistent site-response/soil-structure interaction analysis and evaluation